[RISCV] Define RISC-V specific eflags

[PkmX]

Summary

Add RISC-V eflags as defined in the ABI document:

https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#file-header

[asb]

Thanks, looks good to me!.

include/llvm/BinaryFormat/ELF.h

 #include "ELFRelocs/Hexagon.def"
 };
 
 // ELF Relocation type for Lanai.
 enum {
 #include "ELFRelocs/Lanai.def"
 };
 
+// RISCV Specific e_flags
+enum : unsigned {
+  EF_RISCV_RVC = 0x0001,
+  EF_RISCV_FLOAT_ABI = 0x0006,
+  EF_RISCV_FLOAT_ABI_SOFT = 0x0000,
+  EF_RISCV_FLOAT_ABI_SINGLE = 0x0002,
+  EF_RISCV_FLOAT_ABI_DOUBLE = 0x0004,
+  EF_RISCV_FLOAT_ABI_QUAD = 0x0006,
+  EF_RISCV_RVE = 0x0008
+};
+
 // ELF Relocation types for RISC-V
 enum {
 #include "ELFRelocs/RISCV.def"
 };
 
 // ELF Relocation types for S390/zSeries
 enum {
 #include "ELFRelocs/SystemZ.def"